Devices and methods for measuring light

ABSTRACT

The invention features devices and methods for collecting and measuring light from external light sources. In general, the devices of the invention feature a light diffusing element, e.g., as a component of a light collector, connected by a light conducting conduit, e.g., a fiber optic cable, to a light measuring device, e.g., a spectrometer. This light diffusing element allows, e.g., for substantially uniform light diffusion across its surface and thus accurate measurements, while permitting the total footprint of the device to remain relatively small and portable. This light diffusing element also allows flexibility in scaling of the device to permit use in a wide range of applications.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application Nos.61/698,995, filed Sep. 10, 2012, and 61/784,827, filed Mar. 14, 2013,each of which is hereby incorporated by reference.

FIELD OF THE INVENTION

The invention relates to devices and methods for collecting andmeasuring light.

BACKGROUND OF THE INVENTION

Bench-top integrating spheres are considered the most accurate andreliable devices to collect and subsequently measure light. Thesespheres, however, are relatively large and are not disposed toportability. Other devices, e.g., cosine correctors, become ineffectiveas their size increases, rendering them not viable for certainapplications. This leads to a lack of portable and accurate lightcollecting and measuring devices.

The American Conference of Governmental Industrial Hygienists publishesrecommended maximum daily exposure levels to blue light and UV light.Most manufacturers of dental curing resins supply protective eyewear,but it has been reported that there is a wide range in the effectivenessof this protective eyewear. Current commonly used protectiveglasses/shields may prove inadequate as the radiation intensity of lightcuring units (“LCUs”) further increases. Lack of eye protection may alsooccur if a filter is used to protect against emission from a lamp withproperties other than the lamp for which the filter has been intended.

There is a need in the art to develop a portable device that can quicklycollect and measure light from an external source, e.g., for accuratelymeasuring the performance of the wide range of dental LCUs, which arecurrently being used in dental clinics globally. This type of testingcould then be used to ensure that 1) the LCU being used is appropriatefor the resin composite materials being cured; 2) the LCU's energyoutput is optimized with the time used to ensure that sufficient energyis being delivered to cure the resin materials being used; and 3) theLCU is functioning properly, is not damaged, and/or the light output isnot obstructed by resin or other light obstructing material. Inaddition, there is a need in the art for a light collecting andmeasuring device that can quickly evaluate the effectiveness ofprotective eyewear and/or protective shields used with LCUs in dentalclinics.

SUMMARY OF THE INVENTION

The devices and methods of the present invention satisfy the need in theart described above. The invention features a device that includes: a) alight diffusing element that includes: i) an element including a topportion, a bottom portion, and a side portion, where the top portionincludes a screen, the bottom portion includes an inner surface that issubstantially hemispherical, and the side portion includes an innersurface that is substantially cylindrical, where the side portion isconnected to the top portion and the bottom portion; and ii) an outletport in the side portion, where the outlet port is substantiallyparallel to the top portion and is adjacent to the bottom portion, andwhere the outlet port is configured to receive a light conductingconduit. The device may further include b) a light measuring componentincluding an opening configured to receive the light conducting conduit;and c) the light conducting conduit including a first end and a secondend, where the first end is optically connected to the outlet port ofthe light diffusing element, and the second end is optically connectedto the opening in the light measuring component. In one embodiment, thelight diffusing element may be enclosed within an external shellincluding an inner wall and an outer wall and further includes aconnecting element aligned with the outlet port and further aligned withthe first end of the light conducting conduit. In other embodiments, theinner surface of the side portion of the light diffusing element may beseparated from the inner wall of the external shell by between 1 mm and15 mm (e.g., 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10mm, 11 mm, 13 mm, and 15 mm). In yet another embodiment, the innersurface of the side portion of the light diffusing element may beseparated from the inner wall of the external shell by a distance thatis sufficient to prevent light from penetrating the inner surface of theside portion or the bottom portion of the light diffusing element andinteracting with the inner wall of the external shell, e.g., separatedby the thickness of the material used to construct the light diffusingelement.

In any of the above embodiments, the element allows for substantiallyuniform light diffusion across the inner surfaces. The inner surfacesinclude, e.g., polytetrafluoroethylene (e.g., Teflon® or Spectralon®from Labsphere Inc.), polyoxymethylene (e.g., Delrin®), barium sulfate(e.g.,6080 White Reflectance Coating from Labsphere Inc.) or otherLambertian coating (e.g., Spectraflect® or Duraflect® from LabsphereInc.). The remainder of the light diffusing element may include a solidmaterial, e.g., plastic, ceramic, glass, or metal (e.g., brass).

In any of the above embodiments, the top portion may further include anaperture having a diameter substantially equivalent to or smaller thanthe diameter of the substantially cylindrical inner surface of the sideportion, where the screen covers the aperture. In other embodiments, thetop portion of the light diffusing element may include a solid material,e.g., plastic, ceramic, glass, or metal (e.g., brass).

In any of the above embodiments, the external shell may include a solidmaterial, e.g., plastic, ceramic, glass, or metal (e.g., brass).

In any of the above embodiments, the screen may be substantially square,circular, or disc-shaped and may be sized to cover the side portion ofthe light diffusing element. In particular embodiments the screen may bea disc having dimensions of about 28 mm in diameter (e.g., 10 mm, 15 mm,20 mm, 25 mm, 30 mm, 35 mm, or 40 mm in diameter) and is between 0.1 mmand 5 mm thick (e.g., 0.1 mm, 0.5 mm, 1 mm, 2 mm, 3 mm, or 5 mm thick).

In some embodiments, the screen includes polytetrafluoroethylene (e.g.,Teflon® or SpectraIon® from Labsphere Inc.), polyoxymethylene (e.g.,Delrin®), barium sulfate (e.g., 6080 White Reflectance Coating fromLabsphere Inc.) or other Lambertian coating (e.g., Spectraflect® orDuraflect® from Labsphere Inc.). In other embodiments, the screen mayinclude a transparent or other translucent material. In yet otherembodiments, the screen may be coated with a translucent Lambertiancoating. In further embodiments, the screen may further include aone-way mirror, where the one-way mirror allows light into the lightdiffusing element but substantially blocks light from exiting the lightdiffusing element through the one-way mirror.

In any of the above embodiments, the device may further include a filterabove or below the screen. In one embodiment, the filter above thescreen may cover the aperture of the top portion. In any of the aboveembodiments, the filter may be selected from a group consisting ofglass, a neutral density filter, a band pass filter, and a blue bandpass filter. In any of the above embodiments, the filter may filterwavelengths greater than 500 nm (e.g., 510 nm, 550 nm, 600 nm, 700 nm,or 800 nm). The filter may also physically protect the screen fromdamage, i.e., be located on top of or external to the screen.

In any of the above embodiments, the height of the substantiallycylindrical inner surface of the side portion may be between 1 mm and 50mm (e.g., 1 mm, 2 mm, 5 mm, 10 mm, 15 mm, 20 mm, 25 mm, 30 mm, 35 mm, 40mm, 45 mm, and 55 mm).

In some embodiments, the aperture in the top portion of the lightdiffusing element may have a diameter between 4 mm and 30 mm (e.g., 4mm, 5 mm, 8 mm, 10 mm, 15 mm, 20 mm, 25 mm, and 30 mm). In otherembodiments, the aperture in the top portion of the light diffusingelement may have a diameter between 30 mm and 300 mm (e.g., 30 mm, 50mm, 90 mm, 100 mm, 150 mm, 200 mm, 250 mm, and 300 mm). In a specificembodiment, the diameter of the aperture is about 16 mm.

In any of the above embodiments, the light conducting conduit may havean inner diameter between 10 μm and 1000 μm (e.g., 10 μm, 20 μm, 50 μm,100 μm, 300 μm, 500 μm, 700 μm, and 1000 μm in diameter). In someembodiments, the light conducting conduit may have a length between 1 mmand 300 mm (e.g., 1 mm, 10 mm, 50 mm, 75 mm, 100 mm, 150 mm, 200 mm, 250mm, and 300 mm in length).

In any of the above embodiments, the opening of the light measuringcomponent may be between 10 μm and 1000 μm in diameter (e.g., 10 μm, 20μm, 50 μm, 100 μm, 300 μm, 500 μm, 700 μm, and 1000 μm in diameter). Infurther embodiments, the light measuring component is capable ofmeasuring between 150 nm and 1000 nm wavelengths (e.g., 150 nm, 200 nm,300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, and 1000 nmwavelengths). In some embodiments, the light measuring component iscapable of measuring between 360 nm and 540 nm wavelengths (e.g., 360nm, 400 nm, 420 nm, 440 nm, 480 nm, 500 nm, 520 nm, and 540 nmwavelengths).

In any of the above embodiments, the device further includes an externalhousing enclosing the light diffusing element, the light measuringcomponent, and the light conducting conduit. In one embodiment, theexternal housing may further include a window aligned with the screen ofthe top portion of the light diffusing element. In another embodiment,the external housing may further include an opening adjacent to thelight measuring component, where the opening is configured to receive acable.

In any of the above embodiments, the device may further include aprocessor to which data collected by the light measuring component iscommunicated for analysis.

In any of the above embodiments, the device may further include adisplay that is capable of displaying an indicator.

The invention further features a method for measuring light, includingdirecting light from a light source into the light diffusing element ofa device of the invention, where: a) the light entering the lightdiffusing element diffuses within the light diffusing element; b) aportion of the light diffused within the light diffusing element exitsthe light diffusing element through the outlet port and is transportedthrough the light conducting conduit to the light measuring component;c) the light measuring component measures properties of the lightdelivered from the light conducting conduit to produce data andcommunicates the data to a processor; and d) the processor analyzes thedata and generates an indicator.

In some embodiments of the method, the light measuring component maymeasure visible light, infrared light, or UV light. In otherembodiments, the method may further include use of a light blockingmaterial, and where in step (a) light from the light source passesthrough the light blocking material and enters the light diffusingelement. In any of the above embodiments of the method of the invention,the light source may be capable of curing dental resin. In oneembodiment, the light blocking material may be a shield or pair ofglasses that protect against ocular damage from light generated bydental resin curing tools. In other embodiments, the indicator may bepower, irradiance, or maximum exposure time.

The method of the invention may further include a calibration stepincluding: e) providing a pre-calibrated lamp; f) generating a lightbeam from the pre-calibrated lamp and directing the light beam into thelight diffusing element; g) obtaining an indicator value and comparingthe value to an indicator value associated with the pre-calibrated lamp;h) determining a correction factor based on the comparison made in step(g) above; and i) applying the correction factor obtained in step (h)above in to generate the indicator in step (d) above.

As used herein, the term “light diffusing element” refers to a componentin which light may enter and diffuse.

As used herein, the term “light collector” refers to a device thatincludes a light diffusing element and an external shell.

As used herein, the terms “top portion,” “bottom portion,” and “sideportion” refers to distinct portions of a light diffusing element and donot necessarily describe absolute spatial positions.

As used herein, the term “outlet port” refers to an opening or gapthrough which light may travel.

As used herein, the term “about” refers to within 10% of the recitedvalue. All distances, percentages, and measurements recited herein maybe modified by the term “about.”

As used herein, the term “Lambertian” refers to a diffusely reflectingsurface.

As used herein, the term “screen” refers to an object that is white,translucent, and Lambertian, e.g., a solid layer made from or coatedwith polytetrafluoroethylene (e.g., Teflon® or SpectraIon® fromLabsphere Inc.), polyoxymethylene (e.g., Delrin®), barium sulfate(e.g.,6080 White Reflectance Coating from Labsphere Inc.) or otherLambertian coating (e.g., Spectraflect® or Duraflect® from LabsphereInc.).

As used herein, the term “adjacent” refers to a location within 10 mm ofa reference point, e.g., within 9 mm, 8 mm, 7 mm, 6 mm, 5 mm, 4 mm, 3mm, 2 mm, or even 1 mm.

As used herein, the term “opening” refers to a gap in material, e.g., aslit, an entrance slit, or a narrow aperture.

As used herein, the term “connector” refers to an object that joins twoseparate objects.

As used herein, the term “light measuring component” refers to a devicethat is capable of analyzing the spectral components and/or intensity oflight and producing an electronic signal (either analog or digital),e.g., a spectrometer, or a light meter, or a photometer or a photodiodeor a photomultiplier tube, or a CCD array, or a CMOS sensor or aphotovoltaic device.

As used herein, the term “light conducting conduit” refers to anenclosed path, e.g., a channel, tube, or trough that is capable oftransmitting light, e.g., a fiber optic cable or liquid light guide.

As used herein, the terms “communicates” and “communicated” refer to theact of transferring electronic signals (digital or analog), e.g., viawireless communication, via a USB cable, or through internal circuitry.

As used herein, the term “light blocking material” refers to a materialthat prevents or reduces the passage of light, e.g., visible light or UVlight.

As used herein, the term “indicator” refers to a representation of data,e.g., maximum exposure time, transmitted spectral power, transmittedlight power, or transmitted light intensity.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a light collector.

FIG. 2A is a schematic diagram of the front view of a light collector.Units are in millimeters.

FIG. 2B is a schematic diagram of the top view of a light collector.Units are in millimeters.

FIG. 2C is a schematic diagram of the cross-sectional view of a lightcollector showing the light diffusing element. Units are in millimeters.In some embodiments, the connection point of the light conductingconduit does not scale with the other dimensions of the light collectorif made bigger.

FIG. 3 is a schematic diagram of a light collector, light conductingconduit, and spectrometer. Also depicted are an aperture screen, anoptional filter, and a USB cable capable of connecting, e.g., to alaptop.

FIG. 4 is a schematic diagram of a connecting element. Units are inmillimeters.

FIG. 5A is a schematic diagram of a top view of the top portion of alight diffusing element.

FIG. 5B is a schematic diagram of a side view of the top portion of alight diffusing element.

FIGS. 6A-C are schematic diagrams of a spectrometer, including a highdensity USB port, an SMA connector, and a fiber optic stub.

FIGS. 7A, 7B, and 7C are schematic diagrams of front, top, and sideviews, respectively, of a spectrometer connected to a light collectorvia a light conducting conduit. Units are in millimeters.

FIG. 8 is a schematic diagram depicting a side view, of the externalhousing and its interior with a light collector and spectrometerinstalled.

FIG. 9 is a graph showing a comparison of power and power variationbetween three different light collecting devices, measured using a STSspectrometer.

FIG. 10 is a graph showing transmission spectra of interference (TS600,TS575, TS500, and D1) and color (BG1 & BG12) filters measured by anOcean Optics USB4000 spectrometer through an Ocean Optics FOIS-1 FiberOptic Integrating Sphere.

FIG. 11 is a set of graphs displaying data of weighted blue lightirradiance as a function of distance from a LCU for the palatal andfacial geometries. The graph on the right displays least-square fittedlines of the data.

FIG. 12 is a graph showing the weighted power for all shields and usingQTH, PAC, or LED light curing units as light sources.

FIG. 13 is a graph showing the blue light hazard function for retinalphotochemical damage at different wavelengths of light.

FIGS. 14A-D are a set of graphs showing spectral radiation flux of fourdifferent light sources of different powers (Light 1, Light 2, Light 3,and Light 4, respectively) measured using a light collector (device ofthe invention) or an integrating sphere (Labsphere, Inc., 6 in.). Twodifferent spectrometers were used as indicated (USB-USB4000 and STS-STSvis, both from Ocean Optics).

FIG. 15A-15C are a set of schematic diagrams of a spectrometer. Unitsare in millimeters.

FIG. 16A is a schematic diagram of side view of a fully assembled deviceof the invention showing the relative position of the various parts ofthe device. Units are in inches.

FIG. 16B is a schematic diagram of top view of a fully assembled deviceof the invention showing the relative position of the various parts ofthe device. Units are in inches.

FIGS. 17A-17L are schematic diagrams of a device of the inventionincluding a light diffusing element housed in an external housingwithout an external shell. FIG. 17A shows various views of the externalhousing. FIG. 17B shows various cross-sectional and exploded views ofthe external housing, light diffusing element, and light measuringcomponent. FIG. 17C shows a cross-sectional view of the fastening of thetop and bottom of the external housing (not to scale). FIG. 17D showsthe light diffusing element, light conducting conduit, and lightmeasuring component placed in the bottom of the external housing. FIG.17E shows various views of the bottom of the external housing. FIG. 17Fshows various views of the top of the external housing. FIG. 17G showsvarious views of a rubber gasket for moisture protection around a USBport. FIG. 17H shows various views of a spacer that provides an optionaldistance aid between the light diffusing element and the lightconducting conduit. FIG. 17I shows various views of the light diffusingelement. FIG. 17J shows various views of the light conducting conduit.FIG. 17K shows various views of an exemplary light measuring component.FIG. 17L shows various views of the screen. Units are in millimeters.

DETAILED DESCRIPTION

The invention features devices and methods for collecting and measuringlight from external light sources. In general, the devices of theinvention feature a light diffusing element, e.g., as part of a lightcollector, connected by a light conducting conduit, e.g., a fiber opticcable, to a light measuring component, e.g., a spectrometer. The lightdiffusing element allows for substantially uniform light diffusionacross its surface and accurate measurements, while permitting the totalfootprint of the device to remain relatively small and portable. Thelight diffusing element also allows flexibility in scaling of the deviceto permit use in a wide range of applications.

The devices of the invention may be employed in differentconfigurations. In the simplest configuration, the device includes alight diffusing element that includes top portion (3) that includesscreen (5) and an optional aperture (4); bottom portion (6), whichincludes bottom portion inner surface (7) that is substantiallyhemispherical; and side portion (8), which includes side portion innersurface (9) that is substantially cylindrical. Side portion (8) furtherincludes outlet port (10). The light diffusing element may or may not beenclosed within an external shell (2) to form a light collector. Anexemplary light diffusing element in a light collector is shown in FIGS.1 and 2A-2C.

Referring to FIG. 1, the diameter of aperture (4), dimension (A), may beequivalent to or smaller than the diameter of bottom portion innersurface (7), distance (B). Dimensions (A) and/or (B) may vary, e.g.,between 4 mm and 500 mm, e.g., between 10 mm and 15 mm, between 8 mm and30 mm, between 4 mm and 30 mm, between 20 mm and 25 mm, or between 30 mmand 300mm. In some embodiments, dimensions (A) and/or (B) are about 15mm. In some embodiments, dimensions (A) and/or (B) are, e.g., 4, 5, 6,7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25,26, 27, 28, 29, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 110, 120, 130,140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, 250, 260, 270,280, 290, or 300 mm, or may be between any two of these values. In someembodiments, dimension A is, e.g., 100%, 95%, 90%, 85%, 80%, 75%, 70%,65%, 60%, 55%, 50%, or less than 50% of dimension B.

The distance between a plane tangent to the base of bottom portion innersurface (7) and the bottom of outlet port (10), dimension (C), may beabout half of dimension (B), or 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%,or 70% of dimension (B), or may be between any two of these values. Thedistance between bottom portion inner surface (7) and the internal wallof external shell (2), and/or the distance between side portion innersurface (9) and the internal wall of external shell (2), dimension (D),may vary in accordance with the material and application of the device.In some embodiments, dimension (D) is sufficient to prevent light frompenetrating through light diffusing element (1) and interacting with theinternal surface of external shell (2), e.g., by the thickness of thematerial used to manufacture the side and bottom portions. Dimension (D)may be between 1 mm and 100 mm, e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11,12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29,30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 100 mm, ormay be between any two of these values. In some embodiments, dimension(D) is about 3 mm or greater. The distance from the bottom of screen (5)to the top of outlet port (10), dimension (Y), may be between 1 mm and100 mm, e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17,18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 35, 40, 45, 50, 55,60, 65, 70, 75, 80, 85, 90, 95, or 100 mm, or may be between any two ofthese values. In some embodiments, dimension (Y) may be between 10% and300% of dimension (C), e.g., 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%,90%, 100%, 110%, 120%, 130%, 140%, 150%, 160%, 170%, 180%, 190%, 200%,225%, 250%, 275%, or 300% of C, or may be between any two of thesevalues. In some embodiments, dimension (Y) is about 50%, 100%, or 200%of dimension (C).

The geometrical configuration of light diffusing element (1) permitsaccurate measurement and collection of light independent of the angle atwhich the light enters the element and/or device.

The side, bottom, and top portions may be manufactured from any suitablematerial, e.g., polytetrafluoroethylene (e.g., Teflon® or Spectralon®from Labsphere Inc.), polyoxymethylene (e.g., Delrin®), barium sulfate(e.g.,6080 White Reflectance Coating from Labsphere Inc.) or otherLambertian coating (e.g., Spectraflect® or Duraflect® from LabsphereInc.). These portions may also include other materials, e.g., plastic,ceramic, glass, or metal, on which Lambertian materials are layered orcoated. When the top portion includes an aperture, the portions of thetop not including the screen may be made from any material suitable tohold the screen, e.g., plastic, ceramic, glass, or metal.

The exterior shape of optional external shell (2) may be substantiallycubical, cylindrical, pyramidal, or a rectangular solid. The internalsurface and cavity shape of external shell (2) may vary according to theexternal shape of the light diffusing element, e.g., it may conform tothe exterior shape.

In the descriptions that follow, in some instances, numbered elementsnot shown in a referenced figure are shown in one or more precedingfigures.

Referring to FIGS. 2A-2C, a front view, a top view, and across-sectional view, showing the light diffusing element and externalshell in the light collector are shown. This shell may include externalshell inner surface (21), external shell outer surface (22), and cavity(23) to fit a connection element. External shell (2) may be made of anysolid material, e.g., plastic, ceramic, glass, or metal. Outlet port(10) passes through both the external surface of the light diffusingelement and side portion inner surface (9) of the light diffusingchamber defined by bottom portion inner surface (7) and side portioninner surface (9). Outlet port (10) may be located adjacent to cavity(23) of external shell (2) so as to create a channel from the innersurface of the light diffusing chamber to the outer surface of theexternal shell.

In other embodiments, the light diffusing element is connected to alight measuring device by a light conducting conduit. This device may ormay not be enclosed in an external housing (34). The device may alsoinclude connectors to external processors or computers as are known inthe art, e.g., USB and Ethernet. Alternatively, the device may includehardware for wireless transmission of data. The device may also includea processor or computer within it to analyze data and/or provide anindicator. When an external housing is employed, the light diffusingelement may or may not be enclosed in an external shell (2).

Referring to FIG. 3, light collector (31), which includes lightdiffusing element (1) enclosed in external shell (2), is connected tolight measuring element (32), e.g., a spectrometer, via light conductingconduit (33). At the top of light collector (31) are screen (5) andoptional filter (35). USB cable (36) optionally connects spectrometer(32) to an external computer, e.g., a laptop.

The surface of screen (5), e.g., the material of the surface or acoating applied to the surface, is white, translucent, and Lambertian,e.g., made from or coated with polytetrafluoroethylene (e.g., Teflon® orSpectraIon® from Labsphere Inc.), polyoxymethylene (e.g., Delrin®),barium sulfate (e.g., 6080 White Reflectance Coating from LabsphereInc.) or other Lambertian coating (e.g., Spectraflect® or Duraflect®from Labsphere Inc.). Screen (5) is located above the side and bottomportions of light diffusing element (1) of light collector (31). Whenthe top includes an aperture (4), the screen may be sized to cover atleast aperture (4) of light diffusing element (1). The length of screen(5) may be equal to or greater than the diameter of the substantiallyhemispherical bottom portion. In some embodiments, the device mayinclude a filter, e.g., glass (such as alkali-aluminosilicate sheettoughened glass (Gorilla® glass)), neutral density filter, blue bandfilter, or a filter that filters wavelengths of at least 500 nm. Filter(35) may be located in the top portion of light diffusing element (1)above or below aperture screen (5). In certain embodiments, the filteracts as a physical barrier to protect the screen from damage. When anaperture (4) is present in the top portion, it may include one or moretiered recesses into which the screen (5) and any filter (35) rest. Thetiered recesses provide physical support for the perimeter of the screenand filter. Alternative ways of attaching a screen and/or filter areknown. For example, the screen may be part of a component that screws orclamps to the side and bottom portions. The screen may also be a sheetof material that is compressed against the side portion, e.g., by anexternal housing as shown in FIGS. 17A-17L.

Referring to FIGS. 5A and 5B, FIG. 5A is a top view of top portion (3)of light diffusing element (1), and FIG. 5B is a side view of topportion (3) of light diffusing element (1). Top portion (3) includesgraduated diameters and/or widths, with the base being the largest indiameter and/or width and the top level being the smallest in diameter.In certain embodiments, screen (5) and/or filter (35) are attached,e.g., affixed or screwed, to top portion (3) of light diffusing element(1). If filter (35) is used, it may be attached above or below screen(5) in top portion (3). The top portion may be attached to the rest ofthe device, e.g., via threads (e.g., as shown in FIGS. 5A and 5B).

Light conducting conduit (33) may be, e.g., a fiber optic cable orliquid light conduit. Light conducting conduit (33) may be attached tolight diffusing element (1) and/or external shell (2) so that lightconducting conduit (33) is disposed substantially parallel to screen (5)or aperture (4) while the opening of light conducting conduit (33) issubstantially perpendicular to screen (5) or aperture (4). Lightconducting conduit (33) may be between 1 mm and 500 mm in length, e.g.,1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20,25, 30, 35, 40, 45, 50, 75, 100, 125, 150, 175, 200, 250, 300, 350, 400,450, or 500 mm, or may be between any two of these values. The innerdiameter of light conducting conduit (33) may be between, 50 μm and10,000 μm, e.g., 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 125, 150,200, 250, 500, 1,000, 2,000, 3000, 4,000, 5,000, 6,000, 7,000, 8,000,9,000, or 10,000 μm, or may be between any two of these values. Theinner diameter of light conducting conduit (33) may be selected tooptimize the acceptance angle for a given application and materials.Referring to FIG. 4, the acceptance angle, θ_(max), for a fiber opticcable, e.g., a step-index multimode fiber, is calculated by the indicesof refraction as follows:

NA=n sin θ_(max)=√{square root over (n _(f) ² −n _(c) ²)}

Where n is the refractive index of the medium light is traveling beforeentering the fiber; n_(f) is the refractive index of the fiber core; andn_(c) is the refractive index of the cladding.

Referring to FIG. 4, side views of a connection element, e.g., an SMAconnection element, are shown. The external diameter of the connectionelement may be substantially equivalent to the diameter of outlet port(10) of light diffusing element (1). In some embodiments, the externaldiameter of the connection element and the diameter of outlet port (10)are within 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10% of one another.The connection element may be made out of any solid material, e.g.,plastic, ceramic, glass, or metal.

The light measuring element may be any device capable of analyzing thespectral components and/or intensity of light and encoding theinformation in an electronic signal, e.g., a spectrometer, a lightmeter, a photometer, a photodiode, a photomultiplier tube, a CCD array,a CMOS sensor, or a photovoltaic device. Spectral information may beobtained by using of appropriate filters or a diffracting or refractingelement such as a grating or prism. Referring to FIGS. 6A-6C, devices ofthe invention may employ spectrometer (32) having slit ranges, e.g.,between 1 μm and 1,500 μm, e.g., between 10 μm and 1,000 μm, between 100μm and 500 μm, between 300 μm and 400 μm, and between 360 nm and 540 nm,e.g., 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 150, 200, 250, 300, 350,400, 500, 600, 700, 800, 900, or 1,000 μm, or between any two of thesevalues. Spectrometer (32) may be capable of measuring UV light, visiblelight, and/or infrared light. FIGS. 6B and 6C include a connector, e.g.,an SMA connector, so as to facilitate connection between spectrometer(32) and light conducting conduit (33). Any connector that facilitatesthis connection may be used. In some embodiments of the invention,spectrometer (32) may be replaced with any light measuring component.Exemplary spectrometers are described herein, e.g., as shown in FIGS.15A-15C.

FIGS. 7A-7C show a light collector connected to a spectrometer, whichmay be placed in external housing (34). In these embodiments, a window(37) is aligned over aperture (4) and/or screen (5) of light collector(31) so as to permit light to pass through external housing (34)directly into light diffusing element (1). FIG. 8 schematically shows anexemplary assembled device.

In certain embodiments, external housing (34) may also include a port(38) in proximity to spectrometer (32) so as to allow an externalprocessor, e.g., a computer such as a laptop computer, to connect withspectrometer (32). In these embodiments, a cable, e.g., USB cable (36),may pass through external housing (34). In still other embodiments,spectrometer (32) and/or the assembled device may further include aprocessor and/or display capable of and/or programmed to analyze anddisplay the data obtained by spectrometer (32) and/or light measuringcomponent and/or an indicator related to this data. This internalprocessor and/or display may generate an indicator and/or store thedata.

An exemplary device is shown in FIGS. 17A-17L. In this device, the lightdiffusing element is enclosed in an external housing without an externalshell (FIGS. 17A, B, and D). The light diffusing element (FIG. 17I) isconnected to a light conducting conduit (FIG. 17J) which is alsoconnected to a light measuring component, a spectrometer as depicted(FIG. 17K). The light conducting conduit includes SMA connectors. Asshown in section G of FIG. 17B and section D-D of FIG. 17F, the externalhousing has tiered recesses around the window to accommodate a filter(35), e.g., protective glass, and the screen (5). FIG. 21G shows agasket that can be used to seal around a data port, e.g., mini USB, toseal the external housing from moisture. FIG. 21 H shows a spacer usedto ensure that the light conducting conduit is inserted into the lightdiffusing element at the correct depth.

Calibration and Methods of Use

The devices of the invention may be calibrated before use. Thiscalibration may include transmitting a light beam (e.g., visible light,or infrared light, or UV light) from a calibrated lamp, e.g., a NISTcertified lamp, into light diffusing element (1). The light source canbe one that is capable of curing dental resin. A portion of this lightis transmitted along light conducting conduit (33) into the lightmeasuring component, e.g., spectrometer (32), that measure properties ofthe light and may then generate an indicator, and/or an additionalcommunication step may occur where the data is communicated to anexternal processor (e.g., a computer) for analysis and/or indicatordisplay. This indicator may be power, irradiance, or maximum exposuretime. This indicator value is then compared against the anticipatedindicator value for the calibrated light source. A correction factor maythen be applied to the software and/or programming within the processorto generate an accurate light measurement. Alternatively, the valueobtained by the devices of the invention may be compared to thoseobtained by an integrating sphere, and a correction factor appliedaccordingly.

In some embodiments, the devices of the invention may be used to testthe properties, e.g., transmitted spectral power, transmitted lightpower, transmitted light intensity, and/or maximum safe exposure time,of light through a light blocking material (e.g., a shield or pair ofglasses that protect against ocular damage from light generated bydental resin curing tools). Specifically, this light may be generatedfrom a LCU. Filters, e.g., blue filters, neutral density, or short wavelength, may optionally be used as appropriate to the light source. Thesafety material, e.g., safety glasses and/or shields, can be placed overthe light diffusing element. The light may then be directed through thematerial into the light diffusing element for a duration and/or from adistance representative of the normal use of the light source. Otherparameters may be used as required by the application, and, as discussedabove, the device may be calibrated to each set of parameters ifrequired. The light then diffuses within the light diffusing chamber,and a portion of the light exits the chamber through the port and istransmitted along the light conducting conduit to a light measuringcomponent, where properties of the light are measured. This device thenmay analyze the data and render the required indicator and/or the datafrom measuring the properties of the light are communicated to anexternal processor for analysis and/or indicator display. This method isfurther discussed below in Example 1.

In still other embodiments, the devices of the invention may be usedwith other light generating sources and methods, e.g., those describedin U.S. Pub. Nos. 2012-0171745, 2012-0172478, and 2012-0196122, each ofwhich is hereby incorporated by reference in its entirety.

EXAMPLES

The following examples are intended to illustrate the invention. Theyare not meant to limit the invention in any way.

Example 1

Background: Improperly polymerized dental resin materials have reducedmechanical, hardness, and structural integrity, which lead to reducedlongevity, high replacement costs, and potential exposure to toxicunpolymerized materials. For instance, the average life of resin-basedfillings is six years. A key aspect of light curing is that the dentistmust watch at all times the restoration of the tooth. A high power 1Watt) LCU cures the resin. Because the greatest ocular hazard toblue-light occurs at approximately 440 nm (which is close to the peakwavelength of many light emitting diode curing lights), the dentist mustwear blueblocking glasses or shields to protect both his or her own eyesand the patient's eyes from the blue light and prevent retinal damage.The maximum daily exposure from a high power curing unit with an outputof 1.56 W/cm² is only about 6 seconds when the dentist's eyes are 30 cmaway from tooth.

Dental resin materials generally consist of light sensitive monomersthat polymerize when properly initiated by light in a narrow range ofthe visible blue spectrum. Most lights units emit intense blue light inthe 400-500 nm wavelength range with radiant power that can be in excessof 1 Watt. However, the spectral emissions are different between brandsof LCUs, with some also emitting in the ultraviolet-A (UVA) range(320-400 nm). The ISO 10650-1 standard for halogen curing lights limitsthe irradiance in the 190 nm to 385 nm region to no more than 200mW/cm², but there is no upper irradiance limit in the 400 to 500 nmrange, and some units can deliver in excess of 10 W/cm², which canresult in adverse health effects, especially ocular damage.

FIG. 13 shows the blue light hazard function for retinal photochemicaldamage (American Conference of Government Industrial Hygienists; TLVsand BEIs based on the Documentation of the Threshold Limit Values forChemical Substances and Physical Agents and Biological Exposure Indices;2008, pp 146-154). The function is greater than 0.1 in the spectralrange from 400 nm to 500 nm. The greatest ocular hazard to blue-lightoccurs at approximately 440 nm (which is close to the peak wavelength ofmany light emitting diode curing lights). Blue light transmits throughthe ocular media and is absorbed by the retina; at chronic low levels ofexposure, the blue light amplifies retinal aging and degeneration bycausing photochemical injury to the retinal-pigmented epithelium andchoroid. Clinical manifestations of retinal damage include acutephotoretinitis or, in severe cases, premature age-related maculardegeneration.

Experimental methods: A device of the invention, as shown in FIGS. 2A-2Cand FIGS. 16A-16B, was tested. This device included a light collectorconnected to a spectrometer and encased within an external housing. Thespectrometer used was an STS-VIS spectrometer that is optimized in thevisible region with a slit width of 200 μm and a fiberoptic cable with acore diameter of 400 μm and a length of 10 cm. Protectiveeyewear/shields were placed over the window of the external housing. AnLCU, in particular a dental curing wand, was held approximately 30 cmaway from the protective eyewear/shield. The inner surfaces of the lightdiffusing element were made of polytetrafluoroethylene (Teflon®).

LabVIEW was used as an exemplary programming language to collect thespectra measured by the device and to calculate the maximum exposuretime. Inputs for data collection and analysis include integration time,LCU type (PAC, QTH, or LED) and distance between the operator and thetooth. A “dark” spectrum was measured first with the LCU off, and thenthe transmitted spectrum with the LCU on was measured. The raw andblue-weighted spectra were used to verify that the data collection hasbeen carried out correctly and to provide a visual guide on the signalto noise ratio in the spectra.

Results: FIG. 9 displays a comparison between different light collectingdevices that were measured using a STS spectrometer. The radiant sourcewas an LED based “Allegro” light curing unit. Both the Cosine Corrector(Ocean Optics) and the Light Collector of the present invention had a 1mm thick polytetrafluoroethylene (Teflon®) piece covering theirapertures. The “Integrating Sphere” refers to the Ocean Optics FOIS-1Fiber Optic Integrating Sphere (Ocean Optics, 3 in.). An ideal devicehas the highest power and smallest power variation across LCU positionfrom aperture center, as well as lowest cost. The smallest powervariation was key for this application.

During testing, it was noted that when an LCU was shining through blueblocker glasses or shields, fluorescence with wavelengths greater than500 nm was emitted from the glasses or shields. This fluorescenceentered and scattered within the spectrometer, resulting in a spurioussignal in the spectral range below 500 nm. This spurious signalinterfered with the weakly transmitted blue light. A blue band passfilter was necessary to attenuate the fluorescence.

FIG. 10 depicts transmission spectra of interference (T5600, TS575,TS500, and D1) and color (BG1 & BG12) filters measured by an OceanOptics USB4000 spectrometer through an Ocean Optics FOIS-1 Fiber OpticIntegrating Sphere (Ocean Optics, 3 in.). The reference light source isan incandescent light bulb (60W; 120V). The ideal filter allows 100% ofthe light within the blue region and 0% within the yellow region. In thepresent Example, the results indicate that the color BG1 filter isoptimal for this application.

FIG. 11 displays data of weighted blue light irradiance as a function ofdistance from an LCU for the palatal and facial geometries. The datawere obtained from the literature (Evaluation of ocular hazards from 4types of curing lights, Labrie D, Moe J, Price R B, Young M E, Felix CM. J. Can. Dent. Assoc. 2011; 77:b116) under typical clinicalconditions. These data were used to evaluate the total weighted power asa function of distance for the two geometries. As shown in FIG. 11(right), the data were least-square fitted by straight lines. Theequations are shown below:

WI=WP·C·d ⁸,

and

C=10^(A).

WI is the weighted irradiance in units of μW/cm², WP is the weightedpower in units of μW calculated from the spectral radiant powertransmitted through the glasses and shields and measured by theprototype device, d is the distance between the eyes and the LCU inunits of cm, and A and B are two parameters given in Table 1.

TABLE 1 Palatal Facial Constant LED QTH PAC LED QTH PAC A −0.53602−0.77749 0.48787 −1.30516 −1.34564 −1.3718 B −1.78566 −1.80626 −2.0141−1.858965 −1.9413 −1.78902The maximum acceptable exposure time, t_(max), may be determined asfollows:

$t_{\max} = \frac{E_{limit}}{WI}$

where E_(limit) is equal to 10000 μJ/cm².Evaluation of the Effectiveness of Blueblocker ProtectiveGlasses/shields against Ocular Light Induced Hazards

Table 2 shows a list of seven shields and eight blue-blocker glassestogether with two glasses (A1 and A2) used in the glass blowingindustry.

TABLE 2 ABBRE- MODEL MANU- VIATION NAME LENS MFG# FACTURER S1 Pinnacle —  4575 TotalCare Vision Corporation¹ Saver S2 Round Orange — Inc. w/Kerr Blockers Kerr Corporation¹ Sybron Command S3 Cure-Shield — 9006166Premier Dental Products² S4 Shield VLC — 089-4550 Patterson AngulateDental Supply³ S5 Swiss Master — DT-072 EMS⁴ Light S6 Protective — 20816 Kerr light Corporation¹ shield S7 Orange Shields — 5600011Patterson (Large) Dental Supply³ G1 Light — DZ-011 EMS⁴ protectiongoggles G2 Genesis XC?⁷ Orange ?⁷ Ultraden/ (2-1.7 U 1 uvex?⁷ FT K N CE/3111) G3 Filter Argon/ 60 (Orange) ?⁷ NoIR⁵ KTP-EN207 G4 Ultra- Orange?⁷ Uvex⁶ spec 1000 (140 mm Z87) G5 super fit PC amber/   9178.385 Uvex⁶UV 2-1.2 G6 Ultra- SCT-Orange S0360X Uvex⁶ spec 2000 (130-150 mm Z87.1)G7 skyper SCT-Orange S1933X Uvex⁶ G8 Style #21 - #60 #21 #60 NoIR⁵ LargeFlip- up Clip-ons A1 Astrospec Shade 3.0 S2508 Uvex⁶ OTG 3001 Infra-duraA2 Astrospec Shade 5.0 S2509 Uvex⁶ OTG 3001 Infra-dura ¹1717 WestCollins, Orange, CA 92867 (totalcareprotects.com/kerrdental.com) ²1710Romano Drive, Plymouth Meeting, PA 19462, U.S.A. (premusa.com) ³1205Henri Bourassa Blvd., W. Montreal, Quebec, Canada, H3M 3E6(pattersondental.ca) ⁴Ch. de la Vuarpillière 31, 1260 Nyon, Switzerland(ems-company.com) ⁵6155 Pontiac Trail, South Lyon, MI 48178(noir-medical.com/noirlaser.com) ⁶UVEX ARBEITSSCHUTZ GmbH, WürzburgerStr. 181-189, 90766 Fürth (uvex.com) ⁷The question marks indicateinsufficient information was available to fully describe theglasses/shields.

FIG. 12 illustrates the weighted power for all shields and glasses(Table 2) tested in this Example, with QTH, PAC, and LED light curingunits as light sources. The highest weighted power of 5 mW was collectedusing a PAC LCU and S1 shield, while the lowest power of 0.2 μW wascollected using a LED LCU and S6 shield. These measurements provideevidence of the dynamic range and sensitivity available with the device.

Conclusion: The device and methods tested and described in the presentExample were highly effective in functioning as a means to evaluate theeffectiveness of protective eyewear/shields using the light curing unitsfound in dental clinics.

Example 2

Experimental objective: To demonstrate that a device of the invention(light collector) accurately measures spectral radiant flux, of fourdifferent light sources, as compared to a commercially availableintegrating sphere (Labsphere Inc., 6 in.).

Experimental method: Equal amounts of light from four different lightsources were introduced into either a device of the invention (as shownin FIGS. 2A-2C and FIGS. 7A-7C) or an integrating sphere (LabsphereInc., 6 in.). Spectral radiance flux across 360nm-540 nm wavelengths wasmeasured and recorded for each light source.

Results: The device of the invention collected and measured dataaccurately, from each light source, as compared to a commerciallyavailable integrating sphere (Labsphere Inc., 6 in.). Data for totalspectral radiant flux measurements from each of the light sources, usingthe device of the invention or the integrating sphere (Labsphere Inc., 6in.) are provided in Table 3 and in FIGS. 14A-14D.

TABLE 3 Total Spectral Radiant Flux Measurement Light 1 Light 2 Light 3Light 4 Device Spectrometer (mW) (mW) (mW) (mW) Integrating USB4000 287740 1189 699 Sphere (IS) Integrating STS 288 731 1204 689 Sphere (IS)Light Collector USB4000 291 734 1210 694 (LC) Light Collector STS 298739 1238 714 (LC) Mean 291 736 1210 699 S.D 5 4 21 11 Variance (%) 1.7%0.6% 1.7% 1.5% Light 1: Smartlite IQ (Denstply Caulk); Light 2: EliparS10 (3M ESPE); Light 3: D1 (DXM); Light 4: Bluephase Style (IvoclarVivadent)

Conclusion: The device of the invention accurately measured spectralradiant flux, and these measurements are comparable to those made by acommercially available integrating sphere (Labsphere Inc., 6 in.).

All publications and patents cited in this specification areincorporated herein by reference as if each individual publication orpatent were specifically and individually indicated to be incorporatedby reference. Although the foregoing invention has been described insome detail by way of illustration and example for purposes of clarityof understanding, it will be readily apparent to those of ordinary skillin the art in light of the teachings of this invention that certainchanges and modifications may be made thereto without departing from thespirit or scope of the appended claims.

What is claimed is:
 1. A device comprising: a) a light diffusing elementcomprising: i) an element comprising a top portion, a bottom portion,and a side portion, wherein said top portion comprises a screen, saidbottom portion comprises an inner surface that is substantiallyhemispherical, and said side portion comprises an inner surface that issubstantially cylindrical, and wherein said side portion is connected tosaid top portion and said bottom portion; and ii) an outlet port in saidside portion, wherein said outlet port is substantially parallel to saidtop portion and is adjacent to said bottom portion, and wherein saidoutlet port is configured to receive a light conducting conduit.
 2. Thedevice of claim 1, further comprising: b) a light measuring componentcomprising an opening configured to receive the light conductingconduit; and c) the light conducting conduit comprising a first end anda second end, wherein said first end is optically connected to saidoutlet port of said light diffusing element, and said second end isoptically connected to said opening in said light measuring component.3. The device of claim 1, wherein said light diffusing element isenclosed within an external shell comprising an inner wall and an outerwall and further comprising a connecting element aligned with saidoutlet port and further aligned with said first end of said lightconducting conduit.
 4. The device of claim 3, wherein said inner surfaceof said side portion of said light diffusing element is separated fromsaid inner wall of said external shell by between 1 mm and 15 mm. 5.(canceled)
 6. The device of claim 3, wherein said inner surface of saidside portion of said light diffusing element is separated from saidinner wall of said external shell by a distance that is sufficient toprevent light from penetrating said inner surface of said side portionor said bottom portion of said light diffusing element and interactingwith said inner wall of said external shell.
 7. (canceled)
 8. The deviceof claim 1, wherein said element i) allows for substantially uniformlight diffusion across said inner surfaces.
 9. The device of claim 8,wherein said inner surfaces comprise polytetrafluoroethylene, titaniumdioxide-coated alumina, or polyoxymethylene.
 10. The device of claim 1,wherein said top portion further comprises an aperture having a diametersubstantially equivalent to or smaller than the diameter of saidsubstantially cylindrical inner surface of said side portion, andwherein said screen covers said aperture.
 11. (canceled)
 12. The deviceof claim 1, wherein said screen is substantially square, circular, ordisc-shaped and is sized so as to cover said side portion of said lightdiffusing element.
 13. (canceled)
 14. (canceled)
 15. (canceled)
 16. Thedevice of claim 1, wherein said screen comprisespolytetrafluoroethylene, titanium dioxide-coated alumina, orpolyoxymethylene.
 17. (canceled)
 18. (canceled)
 19. The device of claim1, wherein said screen further comprises a one-way mirror, wherein saidone-way mirror allows light into said light diffusing element butsubstantially blocks light from exiting said light diffusing elementthrough said one-way mirror.
 20. (canceled)
 21. (canceled) 22.(canceled)
 23. (canceled)
 24. (canceled)
 25. (canceled)
 26. The deviceof claim 1, wherein the height of said substantially cylindrical innersurface of said side portion is between 1 mm and 50 mm.
 27. (canceled)28. The device of claim 10, wherein said aperture in said top portion ofsaid light diffusing element has a diameter between 4 mm and 30 mm. 29.(canceled)
 30. (canceled)
 31. The device of claim 1, wherein said lightconducting conduit has an inner diameter between 10 μm and 1000 μm. 32.(canceled)
 33. The device of claim 1, wherein said opening of said lightmeasuring component is between 10 μm and 1000 μm in diameter.
 34. Thedevice of claim 1, wherein said light measuring component is capable ofmeasuring wavelengths between 150 nm and 1000 nm.
 35. (canceled)
 36. Thedevice of claim 2, wherein said device further comprises an externalhousing enclosing said light diffusing element, said light measuringcomponent, and said light conducting conduit.
 37. (canceled) 38.(canceled)
 39. The device of claim 1, wherein said device furthercomprises a processor to which data collected by said light measuringcomponent is transmitted for analysis.
 40. (canceled)
 41. A method formeasuring light, comprising directing light generated by a light sourceinto the light diffusing element of a device of claim 2, wherein a)light entering said light diffusing element diffuses within said lightdiffusing element; b) a portion of said light diffused within said lightdiffusing element exits through said outlet port and is transportedthrough said light conducting conduit to said light measuring component;c) said light measuring component collects data from said light of step(c) and transmits said data to a processor; and d) said processoranalyzes said data and generates an indicator.
 42. The method of claim41, wherein said light measuring component measures visible light,infrared light, or UV light.
 43. (canceled)
 44. (canceled) 45.(canceled)
 46. The method of claim 41, wherein said indicator is power,irradiance, or maximum exposure time.
 47. The method of claim 41,wherein said method further comprises a calibration step comprising: e)providing a pre-calibrated lamp; f) generating a light beam from saidpre-calibrated lamp and directing said light beam into said lightdiffusing element; g) obtaining an indicator value and comparing saidvalue to an indicator value associated with said pre-calibrated lamp;and h) determining a correction factor based on said comparing in step(g); and i) applying said correction factor in generating said indicatorin step (d).